Instead, young coho salmon from this redwood and oak-shaded watershed near Santa Cruz last week were swirling around idly in a lagoon. There has been so little rain that sand has blocked the endangered fish from leaving for the ocean or swimming upstream to spawn.

Scott Creek is one of dozens of streams across California where parched conditions have put fish in immediate danger. With the drought, stream flows have been so low that even months into winter, sandbars have remained closed and waters so shallow that many salmon have had their migratory journeys obstructed.

To prevent further stress to salmon and steelhead, state wildlife officials have closed dozens of rivers and streams to fishing, including all coastal streams west of California 1. A storm that soaked parts of Northern California over the weekend should offer a short respite, but experts say streams like Scott Creek will need several inches of rain a week to stay open and connected to the ocean.

Nowhere is the situation more pressing than on California's North and Central Coast, where a population of only a few thousand coho salmon were already teetering on the edge of extinction.

"This is the first animal that will feel the impacts of the drought," said Jonathan Ambrose, a National Marine Fisheries Service biologist who stood at the sand-blocked mouth of Scott Creek to offer his assessment last week. "It's going to take a lot of rain to bust this thing open. And if they can't get in by the end of February or March, they're gone."

Historically, hundreds of thousands of Central California Coast coho salmon started and ended their lives in creeks that flow from coastal mountains and redwood forests to the coast from Humboldt County to Santa Cruz.

Of those that remain, most at risk are coho salmon from about a dozen streams on the southern end of the species' range in North America. If not for a small hatchery near the town of Davenport keeping the population going and genetically viable, coho salmon would probably already be long gone south of the Golden Gate.

The Central Coast population of coho has plummeted from about 56,000 in the 1960s to fewer than 500 returning adults in 2009. Over the last several years it has hovered around a few thousand, according to estimates from the National Marine Fisheries Service.

The population was listed as federally threatened in 1996 and reclassified as endangered in 2005. A 2012 federal plan estimated its recovery could take 50 to 100 years and cost about $1.5 billion.

"Coho are the fish that are really in trouble in the state right now," said Stafford Lehr, chief of fisheries for the California Department of Fish and Wildlife.

"Right now, they're cut off in many of the streams. They're stuck in pools," Lehr said. "As we move deeper into this drought, every life stage is going to suffer increased mortality."

It's not only Central Coast salmon that are in peril.

To the North, on Siskiyou County's Scott River, more than 2,600 coho salmon returned this winter to spawn _ the highest number since 2007 _ but they encountered so little water they weren't able to reach nine-tenths of tributaries to spawn, said Preston Harris, executive director of the Scott River Water Trust.

In the Sacramento River, the U.S. Fish and Wildlife Service plans to release more than 190,000 hatchery-reared chinook salmon Monday to take advantage of recent rainfall. Commercial fishing groups, however, are urging wildlife officials to consider trucking chinook downstream.

"We're in such extremely low-flow conditions that they might as well dig a ditch and bury these fish rather than trying to put them in a river," said Zeke Grader, executive director of the Pacific Coast Federation of Fishermen's Associations.